Method and apparatus for enabling uplink mimo

ABSTRACT

Methods and apparatuses enabling uplink multiple-input multiple-output (MIMO) are provided. A user equipment (UE) includes a transceiver and a processor operably connected to the transceiver. The transceiver is configured to receive an uplink (UL) grant for an UL transmission. The processor is configured to decode a precoding information field in downlink control information (DCI) associated with the UL grant. The precoding information field includes at least one precoding matrix indicator (PMI) corresponding to a plurality of precoders. The transceiver is further configured to precode a data stream according to the precoders indicated by the precoding information field and transmit the precoded data stream on an UL channel.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.15/491,927, filed Apr. 19, 2017, which claims benefit of priority under35 U.S.C. § 119(e) to: U.S. Provisional Patent Application No.62/327,725 filed Apr. 26, 2016; U.S. Provisional Patent Application No.62/413,725 filed Oct. 27, 2016; U.S. Provisional Patent Application No.62/470,622 filed Mar. 13, 2017; and U.S. Provisional Patent ApplicationNo. 62/483,639, filed Apr. 10, 2017. The contents of theabove-identified patent applications are hereby incorporated byreference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to methods for enabling uplinkmultiple-input multiple-output (MIMO). Such methods can be used when auser equipment is equipped with a plurality of transmit antennas andtransmit-receive units.

BACKGROUND

Wireless communication has been one of the most successful innovationsin modern history. The demand of wireless data traffic is rapidlyincreasing due to the growing popularity among consumers and businessesof smart phones and other mobile data devices, such as tablets, “notepad” computers, net books, eBook readers, and machine type of devices.To meet the high growth in mobile data traffic and support newapplications and deployments, improvements in radio interface efficiencyand coverage is of paramount importance.

A mobile device or user equipment can measure the quality of thedownlink channel and report this quality to a base station so that adetermination can be made regarding whether or not various parametersshould be adjusted during communication with the mobile device. Existingchannel quality reporting processes in wireless communications systemsdo not sufficiently accommodate reporting of channel state informationassociated with large, two dimensional array transmit antennas or, ingeneral, antenna array geometry that accommodates a large number ofantenna elements.

SUMMARY

Various embodiments of the present disclosure provide methods andapparatuses for CSI reporting.

In one embodiment, a user equipment (UE) is provided. The UE includes atransceiver and a processor operably connected to the transceiver. Thetransceiver is configured to receive an uplink (UL) grant for an ULtransmission. The processor is configured to decode a precodinginformation field in downlink control information (DCI) associated withthe UL grant. The precoding information field includes at least oneprecoding matrix indicator (PMI) corresponding to a plurality ofprecoders. The transceiver is further configured to precode a datastream according to the precoders indicated by the precoding informationfield and transmit the precoded data stream on an UL channel.

In another embodiment, a base station (BS) is provided. The BS includesa processor and a transceiver operably connected to the processor. Theprocessor is configured to generate a precoding information field in DCIand generate an UL grant for an UL transmission to a UE. The transceiveris configured to transmit, to the UE, the UL grant via a downlink (DL)channel. The DCI is associated with the UL grant and the precodinginformation field includes at least one PMI corresponding to a pluralityof precoders.

In another embodiment, a method for operating a UE is provided. Themethod includes receiving, by the UE, an UL grant for an ULtransmission. The method also includes decoding, by the UE, a precodinginformation field in DCI associated with the UL grant, where theprecoding information field includes at least one PMI corresponding to aplurality of precoders. The method also includes precoding, by the UE, adata stream according to the precoders indicated by the precodinginformation field. The method also includes transmitting, by the UE, theprecoded data stream on an UL channel.

The present disclosure relates to a pre-5th-Generation (5G) or 5Gcommunication system to be provided for supporting higher data ratesBeyond 4th-Generation (4G) communication system such as Long TermEvolution (LTE).

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it can beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller can beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllercan be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items can be used,and only one item in the list can be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to variousembodiments of the present disclosure;

FIGS. 2A and 2B illustrate example wireless transmit and receive pathsaccording to various embodiments of the present disclosure;

FIG. 3A illustrates an example user equipment according to variousembodiments of the present disclosure;

FIG. 3B illustrates an example base station (BS) according to variousembodiments of the present disclosure;

FIG. 4 illustrates an example beamforming architecture wherein oneCSI-RS port is mapped onto a large number of analog-controlled antennaelements;

FIG. 5 illustrates an example operation of dynamic and semi-dynamicprecoded transmission according to an embodiment of the presentdisclosure;

FIG. 6 illustrates an example downlink (DL) signaling for subbandprecoding and a UE procedure to interpret the precoding information DCIfield according to an embodiment of the present disclosure;

FIG. 7 illustrates several example DL signaling schemes for supportingsubband precoding according to some embodiments of the presentdisclosure;

FIG. 8 illustrates another example DL signaling scheme for supportingsubband precoding according to an embodiment of the present disclosure;

FIG. 9 illustrates a flowchart for an example method wherein a UEreceives an UL grant for UL transmission that includes a PrecodingInformation field associated with a plurality of precoders according toan embodiment of the present disclosure.

FIG. 10 illustrates a flowchart for an example method wherein a BSgenerates a Precoding Information field with at least one PMI for a UE(labeled as UE-k) according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 10, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure can beimplemented in any suitably arranged wireless communication system.

LIST OF ACRONYMS

-   -   2D: two-dimensional    -   MIMO: multiple-input multiple-output    -   SU-MIMO: single-user MIMO    -   MU-MIMO: multi-user MIMO    -   3GPP: 3rd generation partnership project    -   LTE: long-term evolution    -   UE: user equipment    -   eNB: evolved Node B or “eNB”    -   BS: base station    -   DL: downlink    -   UL: uplink    -   CRS: cell-specific reference signal(s)    -   DMRS: demodulation reference signal(s)    -   SRS: sounding reference signal(s)    -   UE-RS: UE-specific reference signal(s)    -   CSI-RS: channel state information reference signals    -   SCID: scrambling identity    -   MCS: modulation and coding scheme    -   RE: resource element    -   CQI: channel quality information    -   PMI: precoding matrix indicator    -   RI: rank indicator    -   MU-CQI: multi-user CQI    -   CSI: channel state information    -   CSI-IM: CSI interference measurement    -   CoMP: coordinated multi-point    -   DCI: downlink control information    -   UCI: uplink control information    -   PDSCH: physical downlink shared channel    -   PDCCH: physical downlink control channel    -   PUSCH: physical uplink shared channel    -   PUCCH: physical uplink control channel    -   PRB: physical resource block    -   RRC: radio resource control    -   AoA: angle of arrival    -   AoD: angle of departure

The following documents and standards descriptions are herebyincorporated by reference into the present disclosure as if fully setforth herein: 3GPP Technical Specification (TS) 36.211 version 12.4.0,“E-UTRA, Physical channels and modulation” (“REF 1”); 3GPP TS 36.212version 12.3.0, “E-UTRA, Multiplexing and Channel coding” (“REF 2”);3GPP TS 36.213 version 12.4.0, “E-UTRA, Physical Layer Procedures” (“REF3”); 3GPP TS 36.321 version 12.4.0, “E-UTRA, Medium Access Control (MAC)Protocol Specification” (“REF 4”); and 3GPP TS 36.331 version 12.4.0,“E-UTRA, Radio Resource Control (RRC) Protocol Specification” (“REF 5”).

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess (NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

FIG. 1 illustrates an example wireless network 100 according to variousembodiments of the present disclosure. The embodiment of the wirelessnetwork 100 shown in FIG. 1 is for illustration only. Other embodimentsof the wireless network 100 could be used without departing from thescope of the present disclosure.

The wireless network 100 includes a base station (BS) 101, a BS 102, anda BS 103. The BS 101 communicates with the BS 102 and the BS 103. The BS101 also communicates with at least one Internet Protocol (IP) network130, such as the Internet, a proprietary IP network, or other datanetwork. Instead of “BS”, an alternative term such as “eNB” (enhancedNode B) or “gNB” (general Node B) can also be used. Depending on thenetwork type, other well-known terms can be used instead of “gNB” or“BS,” such as “base station” or “access point.” For the sake ofconvenience, the terms “gNB” and “BS” are used in this patent documentto refer to network infrastructure components that provide wirelessaccess to remote terminals. Also, depending on the network type, otherwell-known terms can be used instead of “user equipment” or “UE,” suchas “mobile station,” “subscriber station,” “remote terminal,” “wirelessterminal,” or “user device.” For the sake of convenience, the terms“user equipment” and “UE” are used in this patent document to refer toremote wireless equipment that wirelessly accesses a gNB, whether the UEis a mobile device (such as a mobile telephone or smartphone) or isnormally considered a stationary device (such as a desktop computer orvending machine).

The gNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe gNB 102. The first plurality of UEs includes a UE 111, which can belocated in a small business (SB); a UE 112, which can be located in anenterprise (E); a UE 113, which can be located in a WiFi hotspot (HS); aUE 114, which can be located in a first residence (R); a UE 115, whichcan be located in a second residence (R); and a UE 116, which can be amobile device (M) like a cell phone, a wireless laptop, a wireless PDA,or the like. The gNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe gNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the gNBs 101-103 cancommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, or other advanced wireless communication techniques.

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with gNBs, such as the coverage areas 120and 125, can have other shapes, including irregular shapes, dependingupon the configuration of the gNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of gNB 101, gNB 102, andgNB 103 transmit measurement reference signals to UEs 111-116 andconfigure UEs 111-116 for CSI reporting as described in embodiments ofthe present disclosure. In various embodiments, one or more of UEs111-116 receive transmission scheme or precoding information signaled inan uplink grant and transmit accordingly.

Although FIG. 1 illustrates one example of a wireless network 100,various changes can be made to FIG. 1. For example, the wireless network100 could include any number of gNBs and any number of UEs in anysuitable arrangement. Also, the gNB 101 could communicate directly withany number of UEs and provide those UEs with wireless broadband accessto the network 130. Similarly, each gNB 102-103 could communicatedirectly with the network 130 and provide UEs with direct wirelessbroadband access to the network 130. Further, the gNB 101, 102, and/or103 could provide access to other or additional external networks, suchas external telephone networks or other types of data networks.

FIGS. 2A and 2B illustrate example wireless transmit and receive pathsaccording to the present disclosure. In the following description, atransmit path 200 can be described as being implemented in a gNB (suchas gNB 102), while a receive path 250 can be described as beingimplemented in a UE (such as UE 116). However, it will be understoodthat the receive path 250 could be implemented in a gNB and that thetransmit path 200 could be implemented in a UE. In some embodiments, thereceive path 250 is configured to receive transmission scheme orprecoding information signaled in an uplink grant and transmitaccordingly as described in embodiments of the present disclosure.

The transmit path 200 includes a channel coding and modulation block205, a serial-to-parallel (S-to-P) block 210, a size N Inverse FastFourier Transform (IFFT) block 215, a parallel-to-serial (P-to-S) block220, an add cyclic prefix block 225, and an up-converter (UC) 230. Thereceive path 250 includes a down-converter (DC) 255, a remove cyclicprefix block 260, a serial-to-parallel (S-to-P) block 265, a size N FastFourier Transform (FFT) block 270, a parallel-to-serial (P-to-S) block275, and a channel decoding and demodulation block 280.

In the transmit path 200, the channel coding and modulation block 205receives a set of information bits, applies coding (such asconvolutional, Turbo, or low-density parity check (LDPC) coding), andmodulates the input bits (such as with Quadrature Phase Shift Keying(QPSK) or Quadrature Amplitude Modulation (QAM)) to generate a sequenceof frequency-domain modulation symbols. The serial-to-parallel block 210converts (such as de-multiplexes) the serial modulated symbols toparallel data in order to generate N parallel symbol streams, where N isthe IFFT/FFT size used in the gNB 102 and the UE 116. The size N IFFTblock 215 performs an IFFT operation on the N parallel symbol streams togenerate time-domain output signals. The parallel-to-serial block 220converts (such as multiplexes) the parallel time-domain output symbolsfrom the size N IFFT block 215 in order to generate a serial time-domainsignal. The ‘add cyclic prefix’ block 225 inserts a cyclic prefix to thetime-domain signal. The up-converter 230 modulates (such as up-converts)the output of the ‘add cyclic prefix’ block 225 to an RF frequency fortransmission via a wireless channel. The signal can also be filtered atbaseband before conversion to the RF frequency.

A transmitted RF signal from the gNB 102 arrives at the UE 116 afterpassing through the wireless channel, and reverse operations to those atthe gNB 102 are performed at the UE 116. The down-converter 255down-converts the received signal to a baseband frequency, and theremove cyclic prefix block 260 removes the cyclic prefix to generate aserial time-domain baseband signal. The serial-to-parallel block 265converts the time-domain baseband signal to parallel time domainsignals. The size N FFT block 270 performs an FFT algorithm to generateN parallel frequency-domain signals. The parallel-to-serial block 275converts the parallel frequency-domain signals to a sequence ofmodulated data symbols. The channel decoding and demodulation block 280demodulates and decodes the modulated symbols to recover the originalinput data stream.

As described in more detail below, the transmit path 200 or the receivepath 250 can perform signaling for CSI reporting. Each of the gNBs101-103 can implement a transmit path 200 that is analogous totransmitting in the downlink to UEs 111-116 and can implement a receivepath 250 that is analogous to receiving in the uplink from UEs 111-116.Similarly, each of UEs 111-116 can implement a transmit path 200 fortransmitting in the uplink to gNBs 101-103 and can implement a receivepath 250 for receiving in the downlink from gNBs 101-103.

Each of the components in FIGS. 2A and 2B can be implemented using onlyhardware or using a combination of hardware and software/firmware. As aparticular example, at least some of the components in FIGS. 2A and 2Bcan be implemented in software, while other components can beimplemented by configurable hardware or a mixture of software andconfigurable hardware. For instance, the FFT block 270 and the IFFTblock 215 can be implemented as configurable software algorithms, wherethe value of size N can be modified according to the implementation.

Furthermore, although described as using FFT and IFFT, this is by way ofillustration only and should not be construed to limit the scope of thepresent disclosure. Other types of transforms, such as Discrete FourierTransform (DFT) and Inverse Discrete Fourier Transform (IDFT) functions,could be used. It will be appreciated that the value of the variable Ncan be any integer number (such as 1, 2, 3, 4, or the like) for DFT andIDFT functions, while the value of the variable N can be any integernumber that is a power of two (such as 1, 2, 4, 8, 16, or the like) forFFT and IFFT functions.

Although FIGS. 2A and 2B illustrate examples of wireless transmit andreceive paths, various changes can be made to FIGS. 2A and 2B. Forexample, various components in FIGS. 2A and 2B could be combined,further subdivided, or omitted and additional components could be addedaccording to particular needs. Also, FIGS. 2A and 2B are meant toillustrate examples of the types of transmit and receive paths thatcould be used in a wireless network. Other suitable architectures couldbe used to support wireless communications in a wireless network.

FIG. 3A illustrates an example UE 116 according to the presentdisclosure. The embodiment of the UE 116 illustrated in FIG. 3A is forillustration only, and the UEs 111-115 of FIG. 1 could have the same orsimilar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3A does not limit the scope of the presentdisclosure to any particular implementation of a UE.

The UE 116 includes an antenna 305, a radio frequency (RF) transceiver310, transmit (TX) processing circuitry 315, a microphone 320, andreceive (RX) processing circuitry 325. The UE 116 also includes aspeaker 330, a processor 340, an input/output (I/O) interface (IF) 345,an input 350, a display 355, and a memory 360. The memory 360 includesan operating system (OS) program 361 and one or more applications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by a gNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS program 361 stored in the memory 360 in orderto control the overall operation of the UE 116. For example, processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as operations for CQImeasurement and reporting for systems described in embodiments of thepresent disclosure as described in embodiments of the presentdisclosure. The processor 340 can move data into or out of the memory360 as required by an executing process. In some embodiments, theprocessor 340 is configured to execute the applications 362 based on theOS program 361 or in response to signals received from gNBs or anoperator. The processor 340 is also coupled to the I/O interface 345,which provides the UE 116 with the ability to connect to other devicessuch as laptop computers and handheld computers. The I/O interface 345is the communication path between these accessories and the processor340.

The processor 340 is also coupled to the input 350 (e.g., keypad,touchscreen, button etc.) and the display 355. The operator of the UE116 can use the input 350 to enter data into the UE 116. The display 355can be a liquid crystal display or other display capable of renderingtext and/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

As described in more detail below, the UE 116 can perform signaling andcalculation for CSI reporting. Although FIG. 3A illustrates one exampleof UE 116, various changes can be made to FIG. 3A. For example, variouscomponents in FIG. 3A could be combined, further subdivided, or omittedand additional components could be added according to particular needs.As a particular example, the processor 340 could be divided intomultiple processors, such as one or more central processing units (CPUs)and one or more graphics processing units (GPUs). Also, while FIG. 3Aillustrates the UE 116 configured as a mobile telephone or smartphone,UEs could be configured to operate as other types of mobile orstationary devices.

FIG. 3B illustrates an example gNB 102 according to the presentdisclosure. The embodiment of the gNB 102 shown in FIG. 3B is forillustration only, and other gNBs of FIG. 1 could have the same orsimilar configuration. However, gNBs come in a wide variety ofconfigurations, and FIG. 3B does not limit the scope of the presentdisclosure to any particular implementation of a gNB. gNB 101 and gNB103 can include the same or similar structure as gNB 102.

As shown in FIG. 3B, the gNB 102 includes multiple antennas 370 a-370 n,multiple RF transceivers 372 a-372 n, transmit (TX) processing circuitry374, and receive (RX) processing circuitry 376. In certain embodiments,one or more of the multiple antennas 370 a-370 n include 2D antennaarrays. The gNB 102 also includes a controller/processor 378, a memory380, and a backhaul or network interface 382.

The RF transceivers 372 a-372 n receive, from the antennas 370 a-370 n,incoming RF signals, such as signals transmitted by UEs or other gNBs.The RF transceivers 372 a-372 n down-convert the incoming RF signals togenerate IF or baseband signals. The IF or baseband signals are sent tothe RX processing circuitry 376, which generates processed basebandsignals by filtering, decoding, and/or digitizing the baseband or IFsignals. The RX processing circuitry 376 transmits the processedbaseband signals to the controller/processor 378 for further processing.

The TX processing circuitry 374 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 378. The TX processing circuitry 374 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 372 a-372 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 374 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 370 a-370 n.

The controller/processor 378 can include one or more processors or otherprocessing devices that control the overall operation of the gNB 102.For example, the controller/processor 378 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 372 a-372 n, the RX processing circuitry 376, andthe TX processing circuitry 374 in accordance with well-knownprinciples. The controller/processor 378 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. In some embodiments, the controller/processor 378 includes atleast one microprocessor or microcontroller.

The controller/processor 378 is also capable of executing programs andother processes resident in the memory 380, such as an OS. Thecontroller/processor 378 is also capable of supporting channel qualitymeasurement and reporting for systems having 2D antenna arrays asdescribed in embodiments of the present disclosure. In some embodiments,the controller/processor 378 supports communications between entities,such as web RTC. The controller/processor 378 can move data into or outof the memory 380 as required by an executing process.

The controller/processor 378 is also coupled to the backhaul or networkinterface 382. The backhaul or network interface 382 allows the gNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 382 could support communications overany suitable wired or wireless connection(s). For example, when the gNB102 is implemented as part of a cellular communication system (such asone supporting 5G or new radio access technology or NR, LTE, or LTE-A),the interface 382 could allow the gNB 102 to communicate with other gNBsover a wired or wireless backhaul connection. When the gNB 102 isimplemented as an access point, the interface 382 could allow the gNB102 to communicate over a wired or wireless local area network or over awired or wireless connection to a larger network (such as the Internet).The interface 382 includes any suitable structure supportingcommunications over a wired or wireless connection, such as an Ethernetor RF transceiver.

The memory 380 is coupled to the controller/processor 378. Part of thememory 380 could include a RAM, and another part of the memory 380 couldinclude a Flash memory or other ROM. In certain embodiments, a pluralityof instructions, such as a BIS algorithm is stored in memory. Theplurality of instructions are configured to cause thecontroller/processor 378 to perform the BIS process and to decode areceived signal after subtracting out at least one interfering signaldetermined by the BIS algorithm.

As described in more detail below, the transmit and receive paths of thegNB 102 (implemented using the RF transceivers 372 a-372 n, TXprocessing circuitry 374, and/or RX processing circuitry 376) performconfiguration and signaling for CSI reporting.

Although FIG. 3B illustrates one example of a gNB 102, various changescan be made to FIG. 3B. For example, the gNB 102 could include anynumber of each component shown in FIG. 3A. As a particular example, anaccess point could include a number of interfaces 382, and thecontroller/processor 378 could support routing functions to route databetween different network addresses. As another particular example,while shown as including a single instance of TX processing circuitry374 and a single instance of RX processing circuitry 376, the gNB 102could include multiple instances of each (such as one per RFtransceiver).

Rel.13 LTE supports up to 16 CSI-RS antenna ports that enable a gNB tobe equipped with a large number of antenna elements (such as 64 or 128).In this case, a plurality of antenna elements is mapped onto one CSI-RSport. Furthermore, up to 32 CSI-RS ports will be supported in Rel.14LTE. For next generation cellular systems such as 5G, it is expectedthat the maximum number of CSI-RS ports remain more or less the same.

For mmWave bands, although the number of antenna elements can be largerfor a given form factor, the number of CSI-RS ports—which can correspondto the number of digitally precoded ports—tends to be limited due tohardware constraints (such as the feasibility to install a large numberof ADCs/DACs at mmWave frequencies) as illustrated in embodiment 400 ofFIG. 4. In this case, one CSI-RS port is mapped onto a large number ofantenna elements that can be controlled by a bank of analog phaseshifters 401. One CSI-RS port can then correspond to one sub-array thatproduces a narrow analog beam through analog beamforming 405. Thisanalog beam can be configured to sweep across a wider range of angles(420) by varying the phase shifter bank across symbols or subframes. Thenumber of sub-arrays (equal to the number of RF chains) is the same asthe number of CSI-RS ports N_(CSI_PORT). A digital beamforming unit 410performs a linear combination across N_(CSI_PORT) analog beams tofurther increase precoding gain. While analog beams are wideband (hencenot frequency-selective), digital precoding can be varied acrossfrequency sub-bands or resource blocks.

To enable digital precoding, efficient design of CSI-RS is an importantfactor. For this reason, three types of CSI reporting mechanismcorresponding to three types of CSI-RS measurement behavior aresupported in Rel.13 LTE: 1) ‘CLASS A’ CSI reporting that corresponds tonon-precoded CSI-RS, 2) ‘CLASS B’ reporting with K=1 CSI-RS resourcethat corresponds to UE-specific beamformed CSI-RS, 3) ‘CLASS B’reporting with K>1 CSI-RS resources that corresponds to cell-specificbeamformed CSI-RS. For non-precoded (NP) CSI-RS, a cell-specificone-to-one mapping between CSI-RS port and TXRU is utilized. Here,different CSI-RS ports have the same wide beam width and direction andhence generally cell wide coverage. For beamformed CSI-RS, beamformingoperation, either cell-specific or UE-specific, is applied on anon-zero-power (NZP) CSI-RS resource (which includes multiple ports).Here, (at least at a given time/frequency) CSI-RS ports have narrow beamwidths and hence not cell wide coverage, and (at least from the gNBperspective) at least some CSI-RS port-resource combinations havedifferent beam directions.

In scenarios where DL long-term channel statistics can be measuredthrough UL signals at a serving gNB, UE-specific BF CSI-RS can bereadily used. This is typically feasible when UL-DL duplex distance issufficiently small. When this condition does not hold, however, some UEfeedback is used for the gNB to obtain an estimate of DL long-termchannel statistics (or any of its representation thereof). To facilitatesuch a procedure, a first BF CSI-RS transmitted with periodicity T1 (ms)and a second NP CSI-RS transmitted with periodicity T2 (ms), whereT1≤T2. This approach is termed hybrid CSI-RS. The implementation ofhybrid CSI-RS is largely dependent on the definition of CSI process andNZP CSI-RS resource.

In Rel.10 LTE, UL SU-MIMO transmission is supported using acodebook-based transmission scheme. That is, an UL grant (containing DCIformat 4) includes a single PMI field (along with RI) that indicates thesingle precoding vector or matrix (from a predefined codebook) a UEshall use for the scheduled UL transmission. Therefore, when multiplePRBs are allocated to the UE, a single precoding matrix indicated by thePMI implies that wideband UL precoding is utilized. Despite itssimplicity, this is clearly sub-optimal since typical UL channel isfrequency-selective and a UE is frequency scheduled to transmit usingmultiple PRBs.

Yet another drawback of Rel.10 LTE UL SU-MIMO is its lack of support forscenarios where accurate UL-CSI is unavailable at the gNB (which isneeded for properly operating codebook-based transmission). Thissituation can happen in scenarios with high-mobility UEs or burstyinter-cell interference in cells with poor isolation.

Therefore, there is a need for designing new components to enable moreefficient support for UL MIMO for the following reasons. First, thesupport for frequency-selective (or subband) precoding for UL MIMO isdesired whenever possible. Second, UL MIMO should offer competitiveperformance even when accurate UL-CSI is unavailable at the gNB. Third,the proposed UL MIMO solution should be able to exploit UL-DLreciprocity where CSI-RS is utilized by the UE to provide UL-CSIestimation for TDD scenarios.

In the present disclosure, unless stated otherwise, the terms PMI(Precoding Matrix Indicator) and TPMI (transmit PMI) are usedinterchangeably to refer to an UL-related DCI field that indicates anassigned precoder or precoder group that a UE uses for a scheduled ULtransmission. Likewise, unless stated otherwise, the terms RI (RankIndicator) and TRI (transmit RI) are used interchangeably to refer to anUL-related DCI field that indicates an assigned number of layers that aUE uses for a scheduled UL transmission.

The present disclosure includes at least four components for enabling ULMIMO. A first component includes a method for configuring precoded ULtransmission. A second component includes embodiments for supporting ULfrequency-selective precoding. A third component includes a method forenabling reciprocity-based UL MIMO transmission. A fourth componentincludes a method for UL transmission with two waveforms. Names or termsused to represent functionality are example and can be substituted withother names or labels without changing the substance of this embodiment.

For the first component (that is, configuring precoded UL transmission),one example embodiment for facilitating operations in various scenarios,dynamic and semi-dynamic beamforming can be described as follows. In oneembodiment, dynamic beamforming is especially applicable when accurateUL-CSI is available at a gNB or UE (for instance, low UE speeds and goodcell isolation or inter-cell interference coordination). In this case,the UE can transmit data through a narrow directional beam sinceaccurate directional information is accessible. For FDD, the gNB cansignal a choice of beamforming or precoding vector/matrix (orvectors/matrices) to a UE via a DL control channel, such as an UL grant.Upon receiving such precoding information, the UE shall use theassociated precoder or beamformer to transmit the requested UL data tothe gNB. This precoding information is updated dynamically by the gNB.

To support dynamic beamforming, a codebook-based MIMO transmission canbe used where an UL grant (containing a relevant DCI) includes a singleprecoding information (PMI) field (along with RI). This PMI indicatesthe single precoding matrix used by the UE for the scheduled ULtransmission. Therefore, one precoder or beamformed is applied to allscheduled PRB s for that UE.

Semi-dynamic beamforming is especially applicable when UL-CSI quality isimpaired at the gNB or UE (for instance, high UE speeds and poor cellisolation that causes bursty inter-cell interference known as theflash-light effect). In this case, it is more advantageous for the gNBto transmit data through a group of directional beams since the UE canonly indicate an approximate (or a range of) directional information.For this purpose, precoder (beam) cycling within a group of beams eitherin time (across OFDM symbols) or frequency (either across REs, RBs, orgroups of RBs) domain can be employed. This approximate directionalinformation can be signaled to the UE via a DL control channel, such asan UL grant. This information can either be a type of long-termprecoding information or an indicator of a subset of precoders.

For semi-dynamic beamforming, a set of multiple precoders is used inconjunction with a predetermined cycling pattern (or set of cyclingpatterns). Either the cycling pattern or the set of precoders can bespecified and signaled to the UE via an UL grant. The PMI field used fordynamic beamforming can be extended to support semi-dynamic beamformingvia precoder cycling. For rank-1 (one-layer) transmission, thissemi-dynamic beamforming can be concatenated with transmit diversitysuch as SFBC or SFBC-FSTD applied to two or four beams where the numberof beams can constitute to the number of UL antenna ports.

FIG. 5 describes an example operation 500 where UE1 502 and UE2 503 areconnected with a gNB 501. The gNB schedules an UL transmission for theUE1 via an UL grant 1 and the UE2 via an UL grant 2. Upon receiving andsuccessfully decoding the UL grant 1 that contains a grant for UE1 totransmit data using dynamic beamforming, UE1 transmits on the UL usingdynamic beamforming. That is, UE1 precodes its data so that the data istransmitted via one narrow directional beam. The precoder used by UE1 issignaled via a PMI field in the UL grant 1. Upon receiving andsuccessfully decoding the UL grant 2 that contains a grant for UE2 totransmit data using semi-dynamic beamforming, UE2 transmits on the ULusing semi-dynamic beamforming. That is, UE2 precodes its data so thatthe data is transmitted via a plurality of directional beams where thesefour beams are cycled either in time (across OFDM symbols), frequency(across REs or RBs), or both time and frequency. In FIG. 5, fourspatially overlapping beams are shown for illustrative purposes. The setof precoders used by UE1 or the use of four beams in a cycling manner issignaled via a PMI field in the UL grant 2.

In the present disclosure, the terms ‘dynamic beamforming’ and‘semi-dynamic beamforming’ are used for illustrative purposes. Otherterms can also be used to represent the same methods and/orfunctionalities. For example, terms such as ‘transmission scheme 1 or A’and ‘transmission scheme 2 or B’—or ‘transmission mode 1’ and‘transmission mode 2’—can be used to represent the two methods oftransmission, respectively. These two transmission schemes can also beused together with other transmission schemes.

To configure a UE interchangeably with either dynamic or semi-dynamicbeamforming as illustrated in FIG. 5, several optional embodiments arepossible.

In a first embodiment, a UE is configured with either dynamic orsemi-dynamic beamforming semi-statically via higher-layer (such as RRC)signaling. An example of this embodiment is to perform transmissionscheme or transmission mode configuration via at least one RRCparameter. In this case, the value of the RRC parameter indicateswhether the UE is configured with dynamic or semi-dynamic beamforming.

In this first embodiment, the PMI field that is a part of the DCI in theUL grant (previously mentioned above) can be used for both dynamic andsemi-dynamic beamforming. The PMI field can signal different hypothesesdepending on whether the UE is configured with dynamic or semi-dynamicbeamforming. When the UE is configured with dynamic beamforming, the PMIfield indicates the precoding matrix or vector the UE shall use for thegranted UL data transmission. When the UE is configured withsemi-dynamic beamforming, the PMI field can indicate the choice of agroup of precoding matrices or vectors the UE shall use for the grantedUL data transmission.

An example is given in TABLE 1-A where a set of length-M O-timeoversampled DFT vectors is used as a set of possible rank-1 precodersfor M antenna ports. Therefore, a set of (OM−1) precoding vectors isavailable. The RRC or higher-layer parameter indicating whether the UEis configured with dynamic or semi-dynamic beamforming isBeamformingScheme, as an example. When the parameter BeamformingSchemeindicates ‘Dynamic’ (that is, dynamic beamforming), PMI=i indicates thatthe UE is requested to (shall) use precoder v_(i) for UL datatransmission. When the parameter BeamformingScheme indicates‘Semi-dynamic’ (that is, semi-dynamic beamforming), PMI=i indicates thatthe UE is requested to (shall) use precoder group G_(i) (which includesa group of B consecutive precoders) for UL data transmission.Optionally, a group of B non-consecutive precoders can also be used ifthe UL channel angular spread is large.

TABLE 1-A Example PMI table for embodiment 1 Precoder or precoder groupBeamformingScheme = BeamformingScheme = PMI value i ‘Dynamic’‘Semi-dynamic’ 0 ν₀ G₀ 1 ν₁ G₁ 2 ν₂ G₂ . . . . . . . . . 0M − 1 ν_(0M−1)G_(0M−1)

$\begin{matrix}{{v_{i} = {\frac{1}{\sqrt{M}} \times \begin{bmatrix}1 & e^{j\frac{2\pi \; i}{OM}} & e^{j\frac{4\pi \; i}{OM}} & \ldots & e^{j\frac{2\pi \; {({M - 1})}i}{OM}}\end{bmatrix}^{T}}}{G_{i} = \begin{bmatrix}v_{i} & v_{{mod}{({{i + 1},{OM}})}} & \ldots & v_{{mod}{({{i + B - 2},{OM}})}} & v_{{mod}{({{i + B - 1},{OM}})}}\end{bmatrix}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

In a second embodiment, a UE is configured with either dynamic orsemi-dynamic beamforming dynamically via an UL grant transmitted on a DLcontrol channel.

One example of this second embodiment is to utilize one DCI parameter toindicate a choice of transmission scheme or mode (either dynamic orsemi-dynamic) the UE shall use for the granted UL data transmission. Inthis example, the PMI field that is a part of the DCI in the UL grantcan be used for both dynamic and semi-dynamic beamforming. Depending onthe value of this DCI parameter (that is, whether the UE is configuredwith dynamic or semi-dynamic beamforming), a PMI field is also needed.This PMI field indicates the precoding matrix or vector the UE shall usefor the granted UL data transmission when the UE is configured withdynamic beamforming. When the UE is configured with semi-dynamicbeamforming, the PMI field can indicate the choice of a group ofprecoding matrices or vectors the UE shall use for the granted UL datatransmission. This example can be described similarly to TABLE 1A. Butin this case, the higher-layer parameter BeamformingScheme can bereplaced with a DCI field BeamformingScheme that takes value of 0(representing, for example, semi-dynamic beamforming) or 1(representing, for example, dynamic beamforming).

Another example of this second embodiment is to utilize only one PMIfield that is a part of the DCI in the UL grant. In this case, given atotal of N_(H) possible hypotheses associated with the B-bit PMI field(where N_(H)≤2^(B)), some N_(H,d) of the N_(H) hypotheses can beutilized for indicating precoder selection for dynamic beamforming whilethe rest (N_(H,sd)=N_(H)−N_(H,d) hypotheses) can be utilized forindicating the selected group of precoders for semi-dynamic beamforming.This example can be described in TABLE 1-B. Compared to TABLE 1-A, TABLE1-B combines the hypotheses from dynamic and semi-dynamic beamforminginto one set indicated by the PMI field. For this example, the number ofhypotheses associated with the PMI field is twice the number associatedwith the PMI field in the first example of the second embodiment as wellas the first embodiment.

TABLE 1-B Example PMI table for embodiment 2 (second example)Interpretation PMI value i Beamforming scheme Precoder or precoder group0 Dynamic Precoder ν₀ 1 Dynamic Precoder ν₁ 2 Dynamic Precoder ν₂ . . .. . . . . . 0M − 1 Dynamic Precoder ν_(0M−1) 0M Semi-dynamic Precodergroup G₀ 0M + 1 Semi-dynamic Precoder group G₁ 0M + 2 Semi-dynamicPrecoder group G₂ . . . . . . . . . 20M − 1  Semi-dynamic Precoder groupG_(0M−1)

$\begin{matrix}{{v_{i} = {\frac{1}{\sqrt{M}} \times \begin{bmatrix}1 & e^{j\frac{2\pi \; i}{OM}} & e^{j\frac{4\pi \; i}{OM}} & \ldots & e^{j\frac{2\pi \; {({M - 1})}i}{OM}}\end{bmatrix}^{T}}}{G_{i} = \begin{bmatrix}v_{i} & v_{{mod}{({{i + 1},{OM}})}} & \ldots & v_{{mod}{({{i + B - 2},{OM}})}} & v_{{mod}{({{i + B - 1},{OM}})}}\end{bmatrix}}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

Optionally, two-dimensional precoder or codebook (especially relevantfor two-dimensional or rectangular array geometries) can be utilized. Inthis case, a precoder can correspond to a pair of indices (m₁, m₂), eachrepresenting one of the two dimensions. An example rank-1 precoderanalogous to the above can be described in Equation 3 (where v₁ and G₁are defined in Equation 2). Here M₁ and M₂ denote the number of ports ina first and a second dimension, respectively. Likewise, O₁ and O₂ denotethe oversampling factor in a first and a second dimension, respectively.

$\begin{matrix}{\begin{matrix}{v_{m_{1},m_{2}} = {\frac{1}{\sqrt{M_{1}M_{2}}} \times {\begin{bmatrix}1 & e^{j\frac{2\pi \; m_{1}}{O_{1}M_{1}}} & e^{j\frac{4\pi \; m_{1}}{O_{1}M_{1}}} & \ldots & e^{j\frac{2\pi \; {({M - 1})}m_{1}}{O_{1}M_{1}}}\end{bmatrix}^{T} \otimes}}} \\{\begin{bmatrix}1 & e^{j\frac{2\pi \; m_{2}}{O_{2}M_{2}}} & e^{j\frac{4\pi \; m_{2}}{O_{2}M_{2}}} & \ldots & e^{j\frac{2\pi \; {({M - 1})}m_{2}}{O_{2}M_{2}}}\end{bmatrix}^{T}} \\{= {v_{m_{1}} \otimes v_{m_{2}}}}\end{matrix}{G_{m_{1},m_{2}} = {G_{m_{1}} \otimes G_{m_{2}}}}{G_{m_{i}}\begin{bmatrix}v_{m_{i}} & v_{{mod}{({{m_{i} + 1},{O_{i}M_{i}}})}} & \ldots & v_{{mod}{({{m_{i} + B_{i} - 2},{O_{i}M_{i}}})}} & v_{{mod}{({{m_{i} + B_{i} - 1},{O_{i}M_{i}}})}}\end{bmatrix}}} & \left( {{Equation}\mspace{14mu} 3} \right)\end{matrix}$

Optionally, one-dimensional precoder or codebook designed fordual-polarized array configurations can also be utilized. In this case,a precoder with two identical parts (each part associated with onepolarization group) and co-phasing between two polarization groups canbe used. An example one-dimensional 2M-port (each of the twopolarization groups including M ports) rank-1 precoder analogous to theabove can be described in Equation 4. Here, K possible values ofco-phasing are used.

$\begin{matrix}{{v_{i,k} = {\frac{1}{\sqrt{2M}} \times \begin{bmatrix}d_{i} \\{e^{\varphi_{k}}d_{i}}\end{bmatrix}}}{d_{i} = \begin{bmatrix}1 & e^{j\frac{2\pi \; i}{OM}} & e^{j\frac{4\pi \; i}{OM}} & \ldots & e^{j\frac{2\pi \; {({M - 1})}i}{OM}}\end{bmatrix}^{T}}{G_{m} = {\quad{\left\lbrack \begin{matrix}v_{m} & v_{{mod}{({{m + 1},{OM}})}} & \ldots & v_{{mod}{({{m + B - 2},{OM}})}} & v_{{mod}{({{m + B - 1},{OM}})}}\end{matrix} \right\rbrack,{m = {{\left( {K - 1} \right)i} + k}}}}}} & \left( {{Equation}\mspace{14mu} 4} \right)\end{matrix}$

Optionally, two-dimensional precoder or codebook designed fordual-polarized array configurations can also be utilized. An exampletwo-dimensional 2M₁M₂-port (each of the two polarization groupsincluding M₁M₂-ports) rank-1 precoder analogous to the above can bedescribed in Equation 5. The group of beams can be defined similarly interms of the three indices m₁, m₂, k of that the single PMI is composed.

$\begin{matrix}{{v_{m_{1},m_{2},k} = {\frac{1}{\sqrt{2M_{1}M_{2}}} \times \begin{bmatrix}{d_{m_{1}} \otimes d_{m_{2}}} \\{e^{\varphi_{k}}{d_{m_{1}} \otimes d_{m_{2}}}}\end{bmatrix}}}{d_{m_{1}} = \begin{bmatrix}1 & e^{j\frac{2\pi \; m_{1}}{O_{1}M_{1}}} & e^{j\frac{4\pi \; m_{1}}{O_{1}M_{1}}} & \ldots & e^{j\frac{2\pi \; {({M - 1})}m_{1}}{O_{1}M_{1}}}\end{bmatrix}^{T}}{d_{m_{2}} = \begin{bmatrix}1 & e^{j\frac{2\pi \; m_{2}}{O_{2}M_{2}}} & e^{j\frac{4\pi \; m_{2}}{O_{2}M_{2}}} & \ldots & e^{j\frac{2\pi \; {({M - 1})}m_{2}}{O_{2}M_{2}}}\end{bmatrix}^{T}}} & \left( {{Equation}\mspace{14mu} 5} \right)\end{matrix}$

With any of the above codebook options, the DL signaling embodiments tosupport switching between dynamic beamforming and semi-dynamicbeamforming is applicable and can be extended in a straightforwardmanner (since each precoder or codebook corresponds to a single PMI).

For the second component (that is, supporting UL frequency selectiveprecoding), in the above embodiments pertaining to the first component,a single precoder is indicated to a UE to be used for UL transmission.Therefore, for a single allocation, the same precoder is applied to allthe allocated RBs. Optionally, subband precoding can also be supportedby signaling one PMI per subband via an UL grant where one subband caninclude a plurality of contiguous RBs. In this case, the DCI fieldcontaining precoding information includes multiple PMIs, each associatedwith one subband and indicating the choice of precoder from apredetermined codebook.

FIG. 6 illustrates an example DL signaling for subband precoding and UEprocedure to interpret the precoding information DCI field that containsN_(PMI) PMIs (each associated with one subband). The number of PMIsN_(PMI) is interdependent with the subband size P_(SUBBAND) of RBs. Fora given UL resource allocation span (expressed in terms of the number ofRBs RA_(RB)), the number of PMIs can be derived as follows:

$N_{PMI} = {\left\lceil \frac{{RA}_{RB}}{P_{SUBBAND}} \right\rceil.}$

Therefore, for a given UE resource allocation, the number of PMIs doesnot directly depend on the number of RBs allocated to the UE since ULresource allocation can include a plurality of contiguous RBs (asillustrated in 601) or clustered RBs (as illustrated in 602). Instead,it depends on the number of RBs starting from the lowest-indexed to thehighest-indexed RBs within the associated UE resource allocation.Denoting the lowest-indexed and the highest-indexed RBs as RB_(low) andRB_(high), respectively,

$N_{PMI} = {\left\lceil \frac{{RA}_{RB}}{P_{SUBBAND}} \right\rceil = {\left\lceil \frac{{RB}_{high} - {RB}_{low} + 1}{P_{SUBBAND}} \right\rceil.}}$

Optionally,

$N_{PMI} = {\left\lceil \frac{{RA}_{{RB},1}}{P_{SUBBAND}} \right\rceil + \ldots + \left\lceil \frac{{RA}_{{RB},N}}{P_{SUBBAND}} \right\rceil}$

where RA_(RB,i) is the number of RBs in the i-th cluster, can also beused. The two examples given in FIG. 6 represent contiguous resourceallocation (601) and clustered resource allocation (602). HereP_(SUBBAND)=4 is used for illustrative purposes. Although the totalnumber of allocated RBs in 602 is smaller than that in 601, the totalnumber of subbands, hence the number of PMIs

$\left( {N_{PMI} = {\left\lceil \frac{10}{4} \right\rceil = 3}} \right)$

is the same since the DL allocation span is the same for 601 and 602.

There are several DL signaling embodiments for supporting subbandprecoding as illustrated in FIG. 7. The following examples differ inseveral aspects such as whether the associated DCI payload size is fixedor varied with the number of subbands corresponding to the allocated RBs(hence the number of subband PMIs), whether all the PMI components areincluded in the DCI or at least some PMI components are signaled outsidethe DCI (or primary DCI), and/or whether the number of subbandscorresponding to the allocated RBs (hence the number of subband PMIs) isfixed or varied depending on UL resource allocation. When the number ofsubband PMIs is fixed, PMI granularity (subband size) varies dependingon UL resource allocation. Conversely, when PMI granularity (subbandsize) is fixed, the number of subband PMIs caries depending on ULresource allocation.

In a first embodiment 1, as illustrated by DCIs 710, a variable-lengthprecoding information DCI fields 711 and 712 that includes N_(PMI) PMIs(each associated with one subband) are used. In this case, the subbandsize (the number of RBs per subband) is fixed. The number of PMIsN_(PMI) depends on the allocation size as well as the locations ofallocated RBs (for instance, whether the allocated PRBs are contiguousor clustered). Consequently, the size of DCI associated with the ULgrant is variable as well (depending on the number of subbands). Thisincreases the number of blind decoding attempts at the UE. Asillustrated by DCIs 710 of FIG. 7, the length of precoding informationDCI fields 711 and 712 scales depending on the number of PMIs inferredfrom resource allocation information where DCI field 712 representsresource allocation that requires more PMIs than DCI field 711 (such asthe case where more RB s are allocated for DCI field 712 compared to DCIfield 711).

In a second embodiment 2, as illustrated by DCIs 720, a second (orsecond-level) DL control information containing at least precodinginformation (N_(PMI) PMIs) required to support subband precoding isused. In this case, the subband size (the number of RB s per subband) isfixed. The location and size of this precoding information can be madedependent on the resource allocation indicated in an associated ULgrant. In this case, the UE first receives the UL grant and decodes theDCI field that indicates resource allocation. Upon decoding resourceallocation information, the UE decodes the second DL control informationthat contains only precoding information. This precoding informationindicates the precoder that the UE uses for each group of RBs (subband)and hence for each RB allocated for the UE. The length precodinginformation DCI field that includes N_(PMI) PMIs is variable and can beinferred from resource allocation information from the first DL controlinformation. Therefore, the number of blind decoding attempts associatedwith the first DL control information is not increased.

In this embodiment, the first DL control information can be transmittedvia L1 DL control channel (analogous to LTE PDCCH or ePDCCH) usingC-RNTI or UE ID. The second DL control information can be transmittedseparately from the first DL control information wherein itstransmission parameters such as its location (in time and/or frequencydomain) and/or payload size and/or MCS can be inferred from the first DLcontrol information, either implicitly (e.g. from C-RNTI and/or someother UE-specific parameter) or explicitly (indicated in the first DLcontrol information as a DCI field). For the second DL controlinformation, C-RNTI or UE ID can either be used or not used. Asillustrated by DCIs 720 of FIG. 7, the length of precoding informationDCI field scales depending on the number of subband PMIs inferred fromresource allocation information where DCI field 722 represents resourceallocation that requires more PMIs than DCI field 721 (such as the casewhere more RBs are allocated for DCI field 722 compared to DCI field721). Unlike the first embodiment, as illustrated by DCIs 710, however,the length of the first DL control information that contains resourceallocation information remains the same while the length of the secondDL control information varies depending on the required number ofsubband PMIs.

The second DL control information can be transmitted either via an L1 DLcontrol channel (for example, that analogous to LTE PDCCH orePDCCH—hence can be perceived as a second-level DCI) or as a part ofresources/channel used for DL data transmission (such as analogous toLTE PDSCH). It can be located either in the same slot/subframe as, or adifferent slot/subframe from, the slot/subframe where the DCI (orfirst-level DCI, hence the UL grant) is transmitted. Regardless whetherthis second DL control information is transmitted in the form of asecond-level DCI or DL data channel transmission (analogous to LTEPDSCH), CRC can be attached to its information bits to facilitate errordetection at the UE.

In a third embodiment 3, as illustrated by DCI 730), a fixed-lengthprecoding information DCI field 731 that includes a fixed number of PMIsN_(PMI)>1 (each associated with one subband) is used. Therefore, only asingle value of N_(PMI) is allowed. In this case, the subband size (thenumber of RBs per subband) can be variable, depending on resourceallocation (the allocation size as well as the locations of allocatedRBs).

For example, with N_(PMI)=2, only two PMIs (hence two separateprecoders) can be assigned to the UE. The first PMI indicates theprecoder associated with a first subset of allocated RBs and the secondPMI with a second subset of allocated RBs different from the firstsubset—where the first and the second subsets, combined together,constitute to all the RBs allocated to the UE. The number of allocatedRBs for each of the two subsets is thus variable (depending on theresource allocation). Consequently, the size of DCI associated with theUL grant is fixed and the number of RBs associated with each of the twoPMIs is variable. In this case, the number of blind decoding attemptsassociated with the first DL control information is not increased. Asillustrated by DCI 730 of FIG. 7, the length of precoding informationDCI field remains the same since a fixed number of PMIs is used for anyresource allocation (that is, the number of allocated RBs and/or thelocations of allocated RBs).

For the third embodiment, several sub-embodiments pertaining to theinterpretation of each PMI along with the associated subband size can bedescribed as follows.

In a first sub-embodiment, the set/subset of RBs associated with each ofN_(PMI) subbands varies as resource allocation (that is, the number ofallocated RBs and/or the locations of allocated RBs) varies. However,for a given/fixed resource allocation, the set/subset of RBs associatedwith each of N_(PMI) subbands is fixed, predetermined, or configured viahigher-layer signaling. This can be, for example, illustrated in FIG. 6.That is, for a given number and/or location of RBs indicated in the ULresource allocation (RA) field, each subband constitutes to a samenumber and/or subset of PRBs. Thus, there is no need for any additionalindication in the associated UL-related DCI or via any other DLsignaling mechanism.

In a second sub-embodiment, the subband associated with the i-th PMI(PMI, where i=0, 1, . . . , N_(PMI)−1) can be changed and thereforedynamically signaled via the UL-related DCI. In this case only thesubbands for (N_(PMI)−1) PMIs need to be signaled since the subband forthe one remaining PMI can be derived from the RA field and the rest of(N_(PMI)−1) subbands. Therefore, in addition to N_(PMI) PMIs/TPMIs,(N_(PMI)−1) additional fields (each of which indicating the subbandassociated with (N_(PMI)−1) PMIs) are signaled via the UL-related DCI.For example, with N_(PMI)=2, one additional subband indicator field(either for the first or the second PMI) is signaled via UL-related DCI.In one variation of this sub-embodiment, one of the two PMIs (denoted asPMI_(SB,1)) can indicate a precoder only for the RB(s) indicated in theadditional subband indicator field (for example, interpreted asanalogous to the ‘best-M’ subbands wherein the value of M can bedynamically signaled as a part of the additional subband indicator fieldor via MAC CE, else semi-statically configured via higher-layersignaling) whereas the other PMI (denoted as PMI_(SB,2)) can indicate awideband precoder that can be used for all the allocated RBs (indicatedin the resource allocation DCI field). In another variation of thissub-embodiment, one of the two PMIs (denoted as PMI_(SB,1)) can indicatea precoder only for the RB(s) indicated in the additional subbandindicator field (for example, interpreted as analogous to the ‘best-M’subbands wherein the value of M can be dynamically signaled as a part ofthe additional subband indicator field or via MAC CE, elsesemi-statically configured via higher-layer signaling) whereas the otherPMI (denoted as PMI_(SB,2)) can indicate a precoder for the remainingallocated RBs (indicated in the resource allocation DCI field).

To avoid any variation in DCI size which could increase the number of UEblind decodes of DL control signaling, the size of the additionalsubband indicator field can be fixed or configured via higher-layersignaling. Therefore, the number of hypotheses (or, furthermore, the setof hypotheses) associated with the subband indicator field can either befixed or configured via higher-layer signaling. For example, to keep thenumber of subband hypotheses for PMI_(SB,2) to a maximum of N_(HYP),when N_(RB) RBs are allocated to the UE (as indicated in the resourceallocation DCI field), the number of possible subbands (subsets ofN_(RB) RBs) can be fixed or higher-layer configured to be no more thanN_(HYP). If each of these possible subbands is of the same size in termsof the number of RBs and the RBs within each subset are as contiguous aspossible, each of the possible subbands can include approximately

$\left\lfloor \frac{N_{RB}}{N_{HYP}} \right\rfloor$

RBs.

In a fourth embodiment 4, the precoding information DCI field cancontain a maximum of K possible values of the number of PMIs N_(PMI).This embodiment can be perceived as the middle ground between embodiment1 and embodiment 3. In this case, the subband size (the number of RB sper subband) can be variable, depending on resource allocation (theallocation size as well as the locations of allocated RBs). For example,with K=2 and N_(PMI)∈{1,2}, the precoding information DCI field cancontain either 1 PMI or 2 PMIs. When the precoding information DCI fieldcontains 1 PMI, the UE shall use the precoder indicated by the PMI forall its allocated RBs. When the precoding information DCI field contains2 PMIs, the first PMI indicates the precoder associated with a firstsubset of allocated RB s and the second PMI with a second subset ofallocated RBs different from the first subset—where the first and thesecond subsets, combined together, constitute to all the RBs allocatedto the UE. The number of allocated RBs for each of the two subsets isthus variable (depending on the resource allocation).

Consequently, the size of DCI associated with the UL grant is variable(can be one of two possible sizes) and the number of RBs associated witha PMI is variable. This increases the number of blind decoding attemptsat the UE but only by a factor of 2. Embodiment 4 can be illustrated ina similar manner to DCIs 710 of FIG. 7, except that there are only twopossible lengths of precoding information (associated with two values ofN_(PMI)).

For any of the above example embodiments for supporting subbandprecoding, especially for embodiment 2 (DCIs 720 of FIG. 7) wherein asecond DL control information containing subband PMIs is used, one extrahypothesis that indicates that the UE can assume the previously (or mostrecently) signaled precoding information (including PMIs, either awideband component or subband components) for the granted ULtransmission can be included in the DCI (or first-level DCI). Thishypothesis can also indicate that the same precoder(s) (wideband and/orsubband) as signaled in the previously (or most recently) granted ULtransmission can be used.

Several options for signaling this extra hypothesis are possible. First,this hypothesis can be associated with one code point of any otherexistent UL-related DCI field. This is relevant, for instance, when noprecoding information is included in the DCI (or first-level DCI). Someexample DCI fields include Resource Allocation, a DCI field indicatingtransmission scheme, or UL DMRS Information. Second, a dedicated 1-bitDCI field that indicates whether a second DL control informationcontaining precoding information (such as subband PMIs) exists or not.Third, when dual-stage codebook is used (described later in the presentdisclosure), the wideband (first-stage) PMI component can be included inthe DCI (or first-level DCI) and signaled as a first-PMI DCI field. Inthis case, this extra hypothesis can be included as one code point ofthe first-PMI DCI field.

Therefore, when this extra hypothesis is detected at the UE, the UE doesnot attempt to decode a second DL control information that includessubband PMIs and assumes the previously (most recently) signaled andreceived precoding information. This scheme facilitates DL controloverhead saving since the second DL control information (which caninclude subband PMIs) is not signaled, for example, when the gNB/networksees no need for change in UL precoders.

A variation of embodiment 2 (DCIs 720 of FIG. 7) wherein the above extrahypothesis is used can be illustrated in 800 of FIG. 8. In thisillustrative example, the extra hypothesis 805 is signaled as one of thetwo-value information included in the DCI 801 (DL control info 1). Aspreviously disclosed, other options can be used. When this extrahypothesis is signaled (in DCI field 803), the second DL controlinformation (denoted as Precoding info, which includes subband PMIs) isnot signaled. Therefore, upon detecting hypothesis 805, the UE canassume the precoders (PMIs) signaled in the most recent previouslydecoded/received Precoding info (e.g. from the most recentlydecoded/received UL grant). Else, new/updated Precoding info issignaled. In this case, the UE shall receive/decode the second DLcontrol information that includes Precoding info based on the decoded ULresource allocation in the DCI 802 or 803.

Any of the above embodiments for supporting subband precoding isapplicable for dynamic beamforming hence can be combined with amechanism for semi-dynamic beamforming (such as the ones exemplified inTABLEs 1-A and 1-B). That is, dynamic beamforming can be associated witha DL control signaling mechanism for subband precoding whilesemi-dynamic beamforming with a DL control mechanism for indicating agroup of precoders for the purpose of precoder/beamformer cycling.

In addition, when dynamic and semi-dynamic beamforming can be configureddynamically for a UE, it is also possible to configure a UE with eithera single precoder for all the allocated RBs (“wideband” precoding) or asubband precoding via higher-layer (RRC) signaling. In this case, an RRCparameter is used to configure the UE with either “wideband” precoding(single precoder for all the allocated RBs) or subband precoding(possibly a plurality of precoders, each for a subset of the allocatedRBs). For example, a two-valued RRC parameter SubbandPrecodingEnabledcan be used. When its value is ‘TRUE’ or ‘ON’, the UE is configured withsubband precoding. In this case, a plurality of PMIs (including one PMI,depending on the embodiment) according to one of the four aforementionedembodiments for subband precoding can be used. When its value is ‘FALSE’or ‘OFF’, the UE is configured with “wideband” precoding. In this case,one PMI is used regardless of UE resource allocation.

The above example embodiments on the signaling support to facilitateswitching between dynamic and semi-dynamic beamforming as well asembodiments for supporting subband precoding are applicable not onlywith a single-stage precoder structure (and hence a single-stagecodebook), but also with a dual-stage precoder structure (and hence adual-stage codebook).

For the third component (that is, embodiments with dual-stage codebookbased on dual-stage precoder), a precoding vector or matrix isassociated with two indices (for example, i₁ and i₂) where a first indexindicates a wideband component and a second index a possibly subbandcomponent. An example of such a precoder structure is v_(i) ₁ _(,i) ₂=u_(i) ₁ w_(i) ₂ (similar to Rel.12 LTE DL MIMO codebook) where U_(i) ₁is wideband (that is, a single stage-one precoder u_(i) ₁ , hence alsoi₁, is used for all the allocated RBs) and w_(i) ₂ can be eitherwideband or subband (that is, a single stage-two precoder w_(i) ₂ ,hence also i₂, can be used for different allocated RBs) depending onwhether “wideband” precoding or subband precoding is configured for theUE. This pair of indices (i₁,i₂) corresponds to a precoder (eithervector or matrix) in a configured precoding codebook. The first precoderu_(i) ₁ (along with its associated PMI value i₁) can correspond to agroup of precoders where the second precoder w_(i) ₂ (along with itsassociated PMI value i₂) can correspond to either a selection and alinear combination of the group of precoders in u_(i) ₁ . In case ofdual-polarized antenna, the second precoder with w_(i) ₂ (along with itsassociated PMI value i₂) can also contain a co-phasing operation betweentwo polarization groups.

Furthermore, a two-dimensional dual-stage precoder or codebook(especially relevant for two-dimensional or rectangular arraygeometries) can be utilized. In this case, the first PMI value i₁ can becomposed of two indices (i_(1,1),i_(1,2)), each corresponding to one ofthe two dimensions. Therefore, a corresponding precoder structure can bewritten as v_(i) ₁ _(,i) ₂ =u_(i) ₁ w_(i) ₂ =u_(i) _(1,1) _(i) _(1,2)w_(i) ₂ (similar to Rel.13 LTE DL MIMO codebook). Here u_(i) _(1,1)_(,i) _(1,2) is wideband (that is, a single stage-one precoder u_(i)_(1,1) _(,i) _(1,2u) _(i) ₁ hence also (i_(1,1), i_(1,2)), is used forall the allocated RBs) and w_(i) ₂ can be either wideband or subband(that is, a single stage-two precoder w_(i) ₂ , hence also i₂, can beused for different allocated RB s) depending on whether “wideband”precoding or subband precoding is configured for the UE. This group ofindices (i_(1,1),i_(1,2),i₂) corresponds to a precoder (either vector ormatrix) in a configured precoding codebook. The first precoder U_(i)_(1,1) _(,i) _(1,2) (along with its associated PMI value (i_(1,1),i_(1,2))) can correspond to a group of precoders where the secondprecoder w_(i) ₂ (along with its associated PMI value i₂) can correspondto either a selection and a linear combination of the group of precodersin U_(i) _(1,1) _(,i) _(1,2) . In case of dual-polarized antenna, thesecond precoder w_(i) ₂ (along with its associated PMI value i₂) canalso contain a co-phasing operation between two polarization groups.

The following embodiments for dual-stage precoder or codebook apply toboth one- or two-dimensional precoder. For two-dimensional precoder orcodebook structure, the first PMI value i₁ can be composed of twoindices (i_(1,1), i_(1,2)). Therefore, the first-stage precoder can beassociated with these two indices: u_(i) ₁ =u_(i) _(1,1) _(,i) _(1,2) .

For example, to configure a UE interchangeably with either dynamic orsemi-dynamic beamforming for dual-stage precoder, several optionalembodiments analogous to the above embodiments and examples forsingle-stage precoder are possible. For dual-stage precoder or codebook,the pair of PMI values (i₁, i₂) (or (i_(1,1),i_(1,2),i₂) fortwo-dimensional precoder) can offer a natural support for both dynamicand semi-dynamic beamforming. When dynamic beamforming is configured,the PMI signaled to a UE includes both i₁ (which is composed of(i_(1,1), i_(1,2)) for two-dimensional codebook) and i₂. Whensemi-dynamic beamforming is configured, the PMI signaled to a UEincludes only i₁ (which is composed of (i_(1,1), i_(1,2), i₂) fortwo-dimensional precoder). The value of the second precoder w_(i) ₂(along with its associated PMI value i₂) indicates a group of precoderacross that the UE shall perform a cycling for its UL data transmission.

In a first embodiment, a UE is configured with either dynamic orsemi-dynamic beamforming semi-statically via higher-layer (such as RRC)signaling. An example of this embodiment is to perform transmissionscheme or transmission mode configuration via at least one RRCparameter. In this case, the value of the RRC parameter indicateswhether the UE is configured with dynamic or semi-dynamic beamforming.

In this first embodiment, the PMI field that is a part of the DCI in theUL grant (previously mentioned above) can be used for both dynamic andsemi-dynamic beamforming. The PMI field can signal different hypothesesdepending on whether the UE is configured with dynamic or semi-dynamicbeamforming (that is, depending on the setting of the higher-layerparameter that indicates whether the UE is configured with dynamic orsemi-dynamic beamforming, or more generally, the first or the secondtransmission scheme). When the UE is configured with dynamicbeamforming, the PMI field indicates the precoding matrix or vector theUE shall use for the granted UL data transmission. In this case, the PMIfield i includes two indices i₁ (which is composed of (i_(1,1), i_(1,2)for two-dimensional codebook) and i₂ of a codebook. When the UE isconfigured with semi-dynamic beamforming, the PMI field i can indicatethe choice of a group of precoding matrices or vectors the UE shall usefor the granted UL data transmission. In this case, the PMI field iincludes only i₁ of the same codebook.

For example, an RRC or higher-layer parameter BeamformingScheme is usedto indicate whether the UE is configured with dynamic or semi-dynamicbeamforming. When the parameter BeamformingScheme indicates ‘Dynamic’(that is, dynamic beamforming), PMI=(i₁, i₂) indicates that the UE isrequested to (shall) use precoder v_(i) ₁ _(,i) ₂ for UL datatransmission. The PMI pair can either be jointly encoded into one PMIparameter i or be separately indicated as two parameters. When theparameter BeamformingScheme indicates ‘Semi-dynamic’ (that is,semi-dynamic beamforming), PMI=i₁ indicates that the UE is requested to(shall) use precoder group associated with i₁ (for example, u_(i) ₁ )for UL data transmission. For two-dimensional codebook, i₁ is composedof (i_(1,1),i_(1,2)).

In addition, when dynamic and semi-dynamic beamforming can be configuredsemi-statically for a UE via higher-layer signaling, it is also possibleto configure a UE with either a single precoder for all the allocated RBs (“wideband” precoding) or a subband precoding via higher-layer (RRC)signaling. In this case, an RRC parameter is used to configure the UEwith either “wideband” precoding (single precoder for all the allocatedRB s) or subband precoding (possibly a plurality of precoders, each fora subset of the allocated RBs). For example, a two-valued RRC parameterSubbandPrecodingEnabled can be used. When its value is ‘TRUE’ or ‘ON’,the UE is configured with subband precoding. In this case, a pluralityof PMIs (including one PMI, depending on the embodiment) according toone of the four aforementioned embodiments for subband precoding can beused. When its value is ‘FALSE’ or ‘OFF’, the UE is configured with“wideband” precoding. In this case, one PMI is used regardless of UEresource allocation.

In a second embodiment, a UE is configured with either dynamic orsemi-dynamic beamforming dynamically either via a MAC control element(MAC CE) or via an UL grant transmitted on a DL control channel.

One example of this second embodiment is to utilize one DCI parameter toindicate a choice of transmission scheme or mode (either dynamic orsemi-dynamic) the UE shall use for the granted UL data transmission (ormore generally, the first or the second transmission scheme). In thisexample, the PMI field that is a part of the DCI in the UL grant can beused for both dynamic and semi-dynamic beamforming. Depending on thevalue of this DCI parameter (that is, whether the UE is configured withdynamic or semi-dynamic beamforming, or more generally, the first or thesecond transmission scheme), a PMI field is also needed. This PMI fieldindicates the precoding matrix or vector the UE shall use for thegranted UL data transmission when the UE is configured with dynamicbeamforming. When the UE is configured with semi-dynamic beamforming,the PMI field can indicate the choice of a group of precoding matricesor vectors the UE shall use for the granted UL data transmission. A DCIfield BeamformingScheme that takes value of 0 (representing, forexample, semi-dynamic beamforming) or 1 (representing, for example,dynamic beamforming).

Another example of this second embodiment is to utilize only one PMIfield that is a part of the DCI in the UL grant. In this case, given atotal of N_(H) possible hypotheses associated with the B-bit PMI field(where N_(H)≤2^(B)), some N_(H,d) of the N_(H) hypotheses can beutilized for indicating precoder selection for dynamic beamforming whilethe rest (N_(H,sd)=N_(H)−N_(H,d) hypotheses) can be utilized forindicating the selected group of precoders for semi-dynamic beamforming.

To facilitate subband precoding for dual-stage precoder, severaloptional embodiments analogous to the above embodiments and examples inFIGS. 6, 7, and 8 for single-stage precoder can be extended toaccommodate a pair of PMI values (i₁, i₂), where i₁ (which can becomposed of (i_(1,1), i_(1,2), for two-dimensional codebook) is widebandand i₂ subband. In this case, the number of bits associated with i₁(which is composed of (i_(1,1), i_(1,2)) for two-dimensional codebook)remains the same regardless of the number of PMIs or the UE resourceallocation. That is, only one DCI field is needed to signal i₁ (whichcan be composed of (i_(1,1),i_(1,2)) for two-dimensional codebook)regardless of the number of PMIs or the UE resource allocation. Only thenumber of bits associated with i₂ can scale or change depending on thenumber of PMIs or the UE resource allocation. Consequently, theprecoding information includes only one i₁ (which is composed of(i_(1,1),i_(1,2)) for two-dimensional codebook) parameter and possibly aplurality of i₂ (each value of i₂ corresponding to a group of RBs). Inparticular, for embodiment 2 (720 of FIG. 7) wherein a second-level DLcontrol information that includes subband PMIs is used, i₁ can beincluded in the DCI (or first-level DCI) since i₁ (which can be composedof (i_(1,1),i_(1,2)) for two-dimensional codebook) is wideband. Since i₂subband, the subband PMIs included in the second-level DL controlinformation comprises i₂ for all the subbands corresponding to theallocated UL resource.

Any of the embodiments for supporting subband precoding is applicablefor dynamic beamforming hence can be combined with a mechanism forsemi-dynamic beamforming. That is, dynamic beamforming can be associatedwith a DL control signaling mechanism for subband precoding whilesemi-dynamic beamforming with a DL control mechanism for indicating agroup or a set of precoders for the purpose of precoder/beamformercycling.

In addition, when dynamic and semi-dynamic beamforming can be configureddynamically for a UE, it is also possible to configure a UE with eithera single precoder for all the allocated RBs (“wideband” precoding) or asubband precoding via higher-layer (RRC) signaling. In this case, an RRCparameter is used to configure the UE with either “wideband” precoding(single precoder for all the allocated RBs) or subband precoding(possibly a plurality of precoders, each for a subset of the allocatedRBs). For example, a two-valued RRC parameter SubbandPrecodingEnabledcan be used. When its value is ‘TRUE’ or ‘ON’, the UE is configured withsubband precoding. In this case, a plurality of PMIs (including one PMI,depending on the embodiment) according to one of the four aforementionedembodiments for subband precoding can be used. When its value is ‘FALSE’or ‘OFF’, the UE is configured with “wideband” precoding. In this case,one PMI is used regardless of UE resource allocation.

For the fourth component (that is, supporting reciprocity-based ULtransmission), when UL-DL channel reciprocity is feasible such as forTDD scenarios, a UE can obtain an estimate of UL channel from measuringDL CSI-RS. In this case, the UE can calculate its own precoder for agiven resource allocation. This obviates the need for signaling aprecoder information DCI field via a DL control channel.

Thus, in one embodiment (4.1), a DCI of an UL grant can contain only thenumber of transmission layers (that is, the transmission rank) withoutany PMI. It should be noted, however, that although the UE is capable ofobtaining an estimate of UL channel to derive its precoder, thisprecoder calculation can be inaccurate due to the absence of ULinterference information (primarily intra-cell interference, which canonly be obtained at the gNB via SRS measurement). This is especiallyrelevant when UL multi-user MIMO (MU-MIMO). To address this problem,several embodiments are proposed in the present disclosure—one of whichor some combinations can be utilized.

In another embodiment (4.2), precoding information identical or similarto those described in component 2 or 3 can be utilized. That is, a DCIfor UL grant contains precoding information that includes one or aplurality of PMIs depending on whether “wideband” or subband precodingis configured, and/or UE resource allocation. All the embodiments forprecoding information DCI field given in component 2 or 3 apply.

In another embodiment (4.3), a precoding information DCI fieldcontaining only a single field is signaled via a DL control channel.This single field can indicate a group or a set of precoders. This setof precoders can be taken from a predefined codebook and defined as asubset of all the precoders in the codebook. This precoder subsetselection can be done for each rank value that is indicated to the UEvia the transmit RI or TRI. In this case, for a given value of RI (orTRI), the PMI (or TPMI) indicates a precoder subset or group specific tothe value of RI (or TRI). Optionally, this precoder subset selection canbe done across the codebook associated with all the possible values ofRI or TRI). In this case, a single precoder subset or group that caninclude precoders from one codebook (associated with one value ofRI/TRI) or multiple codebooks (associated with multiple values ofRI/TRI) can be defined. Therefore, PMI/TPMI can be interpreted withoutany reference or with only partial reference to RI/TRI.

This precoder group or set can include precoders that the UE shalleither choose or combine from. That is, as the UE can acquire anestimate of the UL channel via CSI-RS by utilizing DL-UL channelreciprocity, this UL channel estimate can then be used to select aprecoder from or derive a precoder from a combination of the precodersubset or group indicated via the PMI. This restriction of a subset ofprecoders can be used (by the gNB) to configure a UE to choose aprecoder considering the knowledge of UL intra-cell interference causedby the gNB scheduling. For example, this choice of precoder couldminimize intra-cell interference caused by this UE to other UEs, orcaused by other UEs to this UE. Optionally, this single field canindicate a group of precoders the UE shall avoid. This avoidance from asubset of precoders can be used (by the gNB) to configure a UE to avoidchoosing a precoder considering the knowledge of UL intra-cellinterference caused by the gNB scheduling. For example, this choice ofprecoder could exacerbate intra-cell interference caused by this UE toother UEs, or caused by other UEs to this UE.

The same signaling mechanism as that used for semi-dynamic beamformingcan be used in this embodiment. For example, if a single-stage precoderor codebook is used, a precoding group DCI signaling mechanism similarto TABLE 1-A or 1-B for semi-dynamic beamforming can be utilized asexemplified in TABLE 2-A. Here G_(p) represents a p-th group of Bprecoders.

TABLE 2-A Example precoding information table for TDD scenario:one-stage precoder PMI value i Precoder group 0 G₀ 1 G₁ 2 G₂ . . . . . .P − 1 G_(P−1)

If a dual-stage precoder or codebook is used, a PMI field in theprecoding information field signaled to a UE includes only the first PMIi₁ (which can be composed of (i_(1,1), i_(1,2)) for two-dimensionalprecoder) that also represents a group of precoders. Such precodinggroup signaling is “wideband”, that is, only one field is signaled forany UE resource allocation.

Any of the above three embodiments can be used for TDD scenario whereinDL-UL channel reciprocity is feasible. Optionally, at least two of thesethree embodiments can be supported and configured for a UE viahigher-layer (RRC) signaling.

When DL CSI-RS is used for UL CSI acquisition (especially for precodercalculation), the UE can be configured with at least one CSI-RS resourcefor this purpose. This CSI-RS resource configuration can be the same asor different from that used for DL CSI acquisition. Typical CSI-RSresource parameters can be included in this resource configuration suchas the number of CSI-RS ports, time-domain behavior (periodic,semi-persistent, or aperiodic), subframe configuration (which includessubframe offset and periodicity—applicable for periodic andsemi-persistent CSI-RS), EPRE (energy per RE) or power level, CSI-RSpattern (within one slot/subframe, which also includes frequencydensity), and when more than one CSI-RS resource can be configured, thenumber of NZP CSI-RS resources (K>1).

If the same CSI-RS resource configuration as that for DL CSI acquisitionis used for UL CSI acquisition, a higher-layer (RRC) parameter can beused to indicate whether the CSI-RS resource configuration correspondsto DL or UL measurement (e.g. either CSI, channel, or interferencemeasurement—note that UL and DL interference profiles are typically notreciprocal). Optionally, this indication can be included in eitherResource setting or Measurement Setting for UL CSI acquisition.Optionally, an indication to differentiate (in its configuration viahigher-layer signaling) the use of this CSI-RS between DL from ULmeasurement can be avoided by configuring a UE with K≥1 CSI-RS resourcesand dynamically signaling a CSI-RS resource index to the UE either via aMAC CE or an UL-related DCI. This CSI-RS resource index indicates whichN (e.g. N=1) out of K configured CSI-RS resources is assigned to the UEfor UL CSI measurement/acquisition. In this case, each of the K CSI-RSresources can be assigned its own parameters (such as the number ofports, subframe configuration when applicable, patterns, etc.)

When a UE is configured with CSI-RS resource for UL CSI measurement, aconstraint can also be imposed for CSI or precoder calculation. Forexample, the number of UE antenna ports assumed for CSI calculationusing DL CSI-RS can be set as the number of SRS antenna ports used for acorresponding SRS resource setting. Another possible constraint the UEcan assume is the bandwidth of CSI-RS transmission. When a CSI-RSresource is configured for UL measurement, its transmission bandwidthcan be set as either the UL transmission bandwidth, the RBs associatedwith UL resource allocation included in an UL-related DCI (especiallyrelevant for aperiodic CSI-RS), or a preconfigured value (signaled viahigher-layer/RRC, MAC CE, or L1 DL control signaling such as DCI).

To facilitate the use of DL-UL channel reciprocity for UL transmission,several optional embodiments can be used.

In one embodiment, additional ‘no PMI’ configuration and/or ‘precoderset/group’ configuration can be added in addition to ‘subband PMI’ (onePMI per subband within the allocated resource/RBs) and ‘wideband PMI’(one PMI representing all the subbands in the allocated resource/RBs).This PMI configuration can be used in conjunction with transmissionscheme configuration.

In another embodiment, a separate UL transmission scheme can be definedin addition to the existing transmission schemes. For example, inaddition to ‘dynamic beamforming’ (or transmission scheme 1) and‘semi-dynamic beamforming’ (or transmission scheme 2, for example,diversity-based transmission scheme), ‘reciprocity-based’ ortransmission scheme 3) can be defined. For example, when a UE isconfigured with ‘reciprocity-based’ transmission scheme (or transmissionscheme 3), the UE can interpret the precoding information (PMI) in anUL-related DCI as an indicator of precoder set/group for the UE. Basedon DL channel measurement from CSI-RS, the UE can acquire an estimate ofthe UL channel via DL-UL channel reciprocity. This UL channel estimatecan then be used to select a precoder from or derive a precoder from acombination of the precoder subset or group indicated via the PMI. Withthis procedure, the UE can calculate a single precoder for all theallocated RBs or one precoder for each of the allocated RBs. Suchprecoder calculation can be specified or left to UE implementation.

In yet another embodiment, a separate configuration can be defined toindicate whether a UE is configured with ‘reciprocity-based’ or‘non-reciprocity-based’ UL transmission or precoder calculation or PMImode or, simply, PMI interpretation. This configuration can be signaledvia higher-layer (RRC) or L1/L2 control signaling (DCI or MAC CE).Likewise, when the UE is configured with ‘reciprocity-based’ operation,the UE can interpret the precoding information (PMI) in an UL-relatedDCI as an indicator of precoder set/group for the UE. Based on DLchannel measurement from CSI-RS, the UE can acquire an estimate of theUL channel via DL-UL channel reciprocity. This UL channel estimate canthen be used to select a precoder from or derive a precoder from acombination of the precoder subset or group indicated via the PMI.Likewise, with this procedure, the UE can calculate a single precoderfor all the allocated RBs or one precoder for each of the allocated RBs.Such precoder calculation can be specified or left to UE implementation.

Embodiment 4.3 of the fourth component is described assuming the use ofa single PMI/TPMI that indicates an assigned precoder subset/group.Consequently, if the UE applies frequency selective precoding to thecorresponding UL transmission, the UE assumes the same precodersubset/group for all the allocated RBs. For high-frequency scenarioswherein the allocated RBs can span a wide frequency range, however, asingle precoder group used for all the allocated RBs may not besufficient. Therefore, in a variation of this embodiment, a plurality ofPMIs/TPMIs can be included in an UL-related DCI wherein each PMI/TPMIindicates a precoder group/subset assignment for a particular subband.That is, the precoder group/subset assignment is frequency-selective.For this variation, any of the embodiments pertaining to the secondcomponent wherein subband PMI/TPMI is signaled in an UL-related DCIapplies. In this case, the subband size or configuration for precodergroup/subset assignment can be the same or different from that forprecoder assignment.

For the fifth component (that is, support two-waveform UL transmission),an UL transmission can support both OFDM (CP-OFDM, that is, OFDM withcyclic prefix) and DFT-S-OFDM (DFT-spread OFDM) where DFT-S-OFDM is usedfor single-stream transmission. In this case, several possibleembodiments can be described as follows.

In one embodiment (5.1), when a UE is configured with UL SU-MIMO, the UEtransmits UL data on physical uplink channel (analogous to LTE PUSCH)using CP-OFDM regardless of the transmission rank (the number oftransmission layers). When a UE is configured with single-streamtransmission (non UL SU-MIMO, without rank adaptation capability), a UEcan be configured with either CP-OFDM or DFT-S-OFDM. This configurationcan be signaled either via higher-layer (RRC) signaling, MAC controlelement (MAC CE), or L1 DL control signaling (included in an UL-relatedDCI).

In one variation of embodiment 5.1 (embodiment 5.2), for single-streamtransmission, instead of receiving a configuration signaling, a UE cansignal (to the network or gNB) its own choice of multiple-access scheme(waveform) via an uplink channel. This signaling can be included eitheras a part of UL data transmission or as a separate UL transmission (suchas that on an UL control channel).

In another variation of embodiment 5.1 (embodiment 5.3), in addition tothe description pertaining to embodiment 5.1, the following additionalUE procedure is supported. When a UE is configured with UL SU-MIMO, afallback transmission scheme of DFT-S-OFDM-based single-streamtransmission is supported. This fallback transmission can be dynamicallyscheduled for the UE via an UL-related DCI different from the one usedfor UL SU-MIMO transmission. The size of this “fallback DCI” can besignificantly smaller than that for UL SU-MIMO transmission and locatedin either a same search space or a different search space (for instance,a common search space) from that for UL SU-MIMO transmission. Thisfallback transmission scheme can be the same or different from that forthe single-stream transmission associated with the non-UL SU-MIMOtransmission. This transmission scheme can be used, for instance, when aUE configured with UL SU-MIMO transmission is in a coverage-limitedsituation.

In another embodiment (5.4), when a UE is configured with UL SU-MIMO,the UE transmits UL data on physical uplink channel (analogous to LTEPUSCH) using CP-OFDM for rank-2 (two-layer transmission) and above. Forrank-1 (one-layer transmission), a UE can be configured to transmit witheither CP-OFDM or DFT-S-OFDM. This configuration can be signaled eithervia higher-layer (RRC) signaling, MAC CE, or L1 DL control signaling.For the last approach (via L1 DL control signaling), an UL-related DCIassociated with UL SU-MIMO transmission includes either a one-bit DCIfield indicating which waveform (CP-OFDM or DFT-S-OFDM) is used when thevalue of RI is one, or these two hypotheses (CP-OFDM or DFT-S-OFDM) arejointly encoded with other hypotheses such as RI and/or precodinghypotheses.

In addition, when the UE transmits with DFT-S-OFDM, a single precoder(frequency non-selective precoder) is used.

For this embodiment, when a UE is configured with single-streamtransmission (non UL SU-MIMO, without rank adaptation capability), a UEcan be configured with either CP-OFDM or DFT-S-OFDM. Likewise, thisconfiguration can be signaled either via higher-layer (RRC) signaling,MAC control element (MAC CE), or L1 DL control signaling (included in anUL-related DCI).

For all the above embodiments, whenever DFT-S-OFDM is used, asingle-carrier version of DFT-S-OFDM (single-carrier FDMA, SC-FDMA)where a UE is configured to transmit on a set of contiguous PRBs can beused.

For all the above embodiments, whenever a single-stream transmission isused, either transmit diversity or a single-port transmission can beused.

The names for UL transmission channels or waveforms are example and canbe substituted with other names or labels without changing the substanceand/or function of this embodiment.

FIG. 9 illustrates a flowchart for an example method 900 wherein a UEreceives an UL grant for an UL transmission that includes a PrecodingInformation field associated with a plurality of precoders according toan embodiment of the present disclosure. For example, the method 900 canbe performed by the UE 116.

The method 900 begins with the UE receiving an UL grant for ULtransmission (step 901) and decoding a Precoding Information field in aDCI that is associated with the UL grant wherein the PrecodingInformation field includes at least PMI corresponding to a plurality ofprecoders (step 902). The composition of the Precoding Information fielddepends on the function of the PMI (step 903). If PMI is used forsubband precoding indication, the number of PMIs is at least equal tothe number of precoders and at least one PMI is associated with asubband that corresponds to at least one RB (step 904). In one option,the number of PMIs can be fixed and the number of RBs per subbanddepends on the allocated RBs as indicated in an UL Resource Allocation(RA) field of the DCI. For example, the number of PMIs is at least twoand the DCI further includes a Subband Indicator field for one of thePMIs. In another option, at least one PMI that is associated with asubband is transmitted separately from the DCI that includes the RAfield. If PMI is used for precoder group indication, the number of PMIsis one and the PMI indicates a group including a plurality of precoders(step 905). In this case, the UE either selects a precoder from thegroup or derives a precoder from a combination of at least two precodersin the group for the granted UL transmission. Based on such function,the precoder for each of the allocated RBs is determined (step 906). TheUE further precodes a data stream that is then transmitted on an ULchannel (step 907). This UL channel can be an UL control channel(analogous to LTE PUCCH), UL data channel (analogous to LTE PUSCH), or acombination of the two.

FIG. 10 illustrates a flowchart for an example method wherein a BSgenerates a Precoding Information field with at least one PMI for a UE(labeled as UE-k) according to an embodiment of the present disclosure.For example, the method 1000 can be performed by the BS 102.

The method 1000 begins with the BS generating, for UE-k, a PrecodingInformation DCI field with at least one PMI (step 1001). The compositionof the Precoding Information field depends on the function of the PMI(step 1002). If PMI is used for subband precoding indication, the numberof PMIs is at least equal to the number of precoders and at least onePMI is associated with a subband that corresponds to at least one RB(step 1003). In one option, the number of PMIs can be fixed and thenumber of RBs per subband depends on the allocated RBs as indicated inan UL Resource Allocation (RA) field of the DCI. For example, the numberof PMIs is at least two and the DCI further includes a Subband Indicatorfield for one of the PMIs. In another option, at least one PMI that isassociated with a subband is transmitted separately from the DCI thatincludes the RA field. If PMI is used for precoder group indication, thenumber of PMIs is one and the PMI indicates a group including aplurality of precoders (step 1004). Based on such function, the BSgenerates the UL grant with the DCI for UL transmission to UE-k (step1005) and transmits the UL grant to UE-k on a DL channel (step 1006).This transmission can be done via a DL control channel (analogous to LTEPDCCH or ePDCCH) or a combination between DL control channel and DL datachannel (analogous to LTE PDSCH).

Although FIGS. 9 and 10 illustrate examples of methods for receivingconfiguration information and configuring a UE, respectively, variouschanges could be made to FIGS. 9 and 10. For example, while shown as aseries of steps, various steps in each figure could overlap, occur inparallel, occur in a different order, occur multiple times, or not beperformed in one or more embodiments.

Although the present disclosure has been described with an exampleembodiment, various changes and modifications can be suggested by or toone skilled in the art. It is intended that the present disclosureencompass such changes and modifications as fall within the scope of theappended claims.

1. (canceled)
 2. A user equipment (UE) comprising: a transceiverconfigured to receive, from a base station (BS), configurationinformation that includes a selected uplink (UL) transmission scheme andat least one reference signal (RS) resource; and a processor operablyconnected to the transceiver, the processor configured to: decode theconfiguration information; determine the selected UL transmissionscheme; and determine the at least one RS resource for an UL precodercalculation, wherein the selected UL transmission scheme is one of an ULtransmission without precoding matrix indicator (PMI) and an ULtransmission with PMI, and wherein the at least one RS resourcecorresponds to a channel state information RS (CSI-RS).
 3. The UE ofclaim 2, wherein the configuration information is conveyed viahigher-layer or radio resource controller (RRC) signaling.
 4. The UE ofclaim 2, wherein the CSI-RS resource is used for the UL precodercalculation when the selected UL transmission scheme corresponds to theUL transmission without the PMI in an UL-related downlink controlinformation (DCI).
 5. The UE of claim 4, wherein the UE is configuredwith only one CSI-RS resource for the UL precoder calculation.
 6. The UEof claim 5, wherein the UE is further configured with at least onesounding RS (SRS) resource.
 7. The UE of claim 5, wherein the UE isfurther configured with four sounding RS (SRS) resources.
 8. The UE ofclaim 4, wherein the UE is configured with more than one CSI-RS resourcefor the UL precoder calculation.
 9. A base station (BS) comprising: aprocessor configured to: generate, for a user equipment (UE),configuration information that includes a selected uplink (UL)transmission scheme and at least one reference signal (RS) resource; anda transceiver operably connected to the processor, the transceiverconfigured to: transmit, to the UE, the configuration information; andtransmit, to the UE, an UL-related downlink control information (DCI),wherein the selected UL transmission scheme is one of an UL transmissionwithout precoding matrix indicator (PMI) and an UL transmission withPMI, and wherein the at least one RS resource corresponds to a channelstate information RS (CSI-RS).
 10. The BS of claim 9, wherein theconfiguration information is conveyed via higher-layer or radio resourcecontroller (RRC) signaling.
 11. The BS of claim 9, wherein the CSI-RSresource is used for an UL precoder calculation if the selected ULtransmission scheme corresponds to the UL transmission without the PMIin the UL-related DCI.
 12. The BS of claim 11, wherein the UE isconfigured with only one CSI-RS resource for the UL precodercalculation.
 13. The BS of claim 12, wherein the UE is furtherconfigured with at least one sounding RS (SRS) resource.
 14. The BS ofclaim 12, wherein the UE is further configured with four sounding RS(SRS) resources.
 15. A method for operating a user equipment (UE), themethod comprising: receiving, from a base station (BS), configurationinformation that includes a selected uplink (UL) transmission scheme andat least one reference signal (RS) resource for precoder calculation;decoding the configuration information; and determining the selected ULtransmission scheme and the at least one RS resource for an UL precodercalculation, wherein the selected UL transmission scheme is one of an ULtransmission without precoding matrix indicator (PMI) and an ULtransmission with PMI, and wherein the at least one RS resourcecorresponds to a channel state information RS (CSI-RS).
 16. The methodof claim 15, wherein the configuration information is conveyed viahigher-layer or radio resource controller (RRC) signaling.
 17. Themethod of claim 15, wherein the CSI-RS resource is used for the ULprecoder calculation when the selected UL transmission schemecorresponds to the UL transmission without the PMI in an UL-relateddownlink control information (DCI).
 18. The method of claim 17, whereinthe UE is configured with only one CSI-RS resource for the UL precodercalculation.
 19. The method of claim 18, wherein the UE is furtherconfigured with at least one sounding RS (SRS) resource.
 20. The methodof claim 18, wherein the UE is further configured with four sounding RS(SRS) resources.
 21. The method of claim 17, wherein the UE isconfigured with more than one CSI-RS resource for the UL precodercalculation.